Mr Lee is the fifth person associated with the Causeway Bay Bookstore to go missing.

Two of the other four men were last seen in Shenzhen, where their wives live; one was last seen in Hong Kong; and the other, the owner of a publishing house linked to the bookstore, was last heard from by email from Pattaya, Thailand, where he owns a holiday home.

Mr Lee spoke to the BBC when his four colleagues went missing, but was so worried about reprisals from China that he declined to give his full name.

There is no official word on why the five are missing, but the bookshop they are all linked to stocks publications critical of the Chinese government. [Source]

When the four other publishers disappeared last autumn Lee had said he was a shareholder in the Mighty Current publishing company.

“I think (it has happened) probably because of publishing matters… political books banned on the mainland,” he said at the time.

The other men who went missing are Gui Minhai, a Swedish national and co-owner of the Mighty Current publishing company. Local media said he failed to return from a holiday in Thailand in October.

The publishing company’s general manager Lui Bo, an employee Cheung Jiping and bookstore manager Lam Wing-kei are also reportedly missing after disappearing in southern China in October.

Rights groups had expressed concern at the previous disappearances, with Human Rights Watch saying there was a “concerted effort” by the mainland to prevent Chinese political books travelling from Hong Kong to China. [Source]

What we do know about the case is disturbing enough. Lee publishes and sells politically sensitive books banned on the mainland. Four of his colleagues have gone missing since October in Shenzhen and Thailand.

The Immigration Department has no record of Lee leaving Hong Kong and his home return permit was left at home. Yet, he has called his wife in Hong Kong several times from phone numbers listed in Shenzhen. So the possibility that Lee was taken from Hong Kong and clandestinely sent across the border cannot be ruled out.

Even the government is taking this possibility seriously. John Lee Ka-chiu, the acting secretary for security, admitted police were using established channels with its mainland security counterparts to determine if any Hong Kong resident was being detained.

Raymond Tam Chi-yuen, secretary for constitutional and mainland affairs, when commenting on Lee’s case, said all mainland departments must follow “one country two systems”. [Source]